A liquid crystal display device typically includes a lower substrate including a color filter and an ITO pixel electrode; an active circuit portion including a liquid crystal layer, a thin film transistor, and a condensing capacitor layer; and an upper substrate with an ITO pixel electrode formed therein.
The color filter includes colored layers of red, green and blue or a black light blocking layer. The colored layers represent a color by transmitting light having a particular wavelength. The light blocking layer blocks light which is transmitted out of a transparent pixel electrode of a substrate and not controlled in order to prevent contrast from being deteriorated by the light transmitted through the thin film transistor.
The color filter can be fabricated using a pigment dispersion method by repeating a series of processes: coating a transparent substrate with a photopolymerizable composition including a colorant, performing an exposure to form a pattern of a desired shape, removing unexposed part with a solvent, and performing a thermosetting process.
However, when a photosensitive polyimide or a phenol-based resin is used as a binder resin in the pigment dispersion method, there can be drawbacks such as high heat resistance, low sensitivity, and the use of an organic solvent for development. In addition, a conventional system using an azide compound as a photoresist agent can have problems such as low sensitivity, poor heat resistance, and sensitivity to oxygen during exposure.
An acrylic-based resin can have excellent heat resistance, contraction resistance, and chemical resistance but also can have poor sensitivity, developability, and close contacting (adhesion) property. Moreover, when the light blocking layer includes a large amount of black pigment to meet the required optical density, there can be significant deterioration in the sensitivity, developability and close contacting property.